To Canada -- Priority is expensive (but not nearly as bad as Australia!). First class mail to Canada and many other countries is now tracked. Zero insurance but nobody gets anything from a postal insurance claim anyways.
For example of Canadian tracking -- see:
https://tools.usps.com/go/TrackConfirmAction_input?strOrigTrackNum=LZ172396442US
If mailing several per week - look into a service such as Endicia. Insurance that *really* pays plus at a fraction of the cost of the insurance from USPS.